Vacuum switch



Aug- 1938- w. J. MEANS 2,128,427

VACUUM SWITCH Filed Sept. 26, 1936 lNVENTOR W J. MEANS By Tmhw ATTORNEPPatented ug. so, was

UNITED STATES PATENT OFFICE VACUUM SWITCH Application September as,1936, Serial No. 102,691

9 Claims.

This invention relates to a vacuum contact switch and more particularlyto mechanism for obtaining and maintaining uniform contact pressure insuch a switch.

Insofar as is known, the usual methods for operating the contact arm ofvacuum contact switches comprises the use of a cam directly asscciatedwith the contact arm as shown in Patents 1,836,654 to W. Dom et al., and1,997,288 to H. F. Anderson. This appears to be satisfactory in amajority of devices with which a switch of this character is employed,since the number of operations per day is not great. However, where themovable arm is constantly and rapidly operated as, for example, in aninterrupter, uniform contact pressure and long life are extremelydimcult to obtain without critical adjustments and costly maintenance.When the movable contact arm is directly associated with the surface ofa cam a degree of contact pressure is obtained by flexing the movablearm which is unreliable insofar as contact pressure is concerned, andalso places undue strain upon the diaphragm support for the arm In someinstances, flexibility has been obtained by using a flexible glassenvelope and glass rods directly associated with a cam for operating thecontacts. In an ar= rangement of this character, the contact pressure isuncertain, since the glass supports for the contacts and the movable armor arms cannot be accurately positioned. The life of the contact switchparts in a switch of this character is comparatively short when used asan interrupter.

It is therefore an object of the present invention to provide operatingmechanism for a vacuum contact switch arranged to produce and. maintaina definite gram pressure between the contacts and the switch.

It is a further object of the invention to provide a flexible diaphragmfor supporting the movable contact arm and provide cold cathode glowdischarge tubes for contact protection means to insure long life of acontinuously operating vacuum contact switch and to assist in obtainingand maintaining an exact contact pressure between the contacts of theswitch.

These objects are set forth in a specific embodiment of the inventionfor a ringing current interrupter in which the contact of the movablecontact arm is pressed against a stationary contact within the evacuatedcontainer by an ex.- ternal spring which 'is operable only when thepressure of another spring is removed. In this embodiment, the movablecontact within the 'work or envelope.

evacuated container is maintained an equal distance irom each stationarycontact by two opposed external springs of equal stiffness which engagethe movable contact arm. A rotating cam is used to remove the pressureof one spring 6 against the other by successively flexing alternatesprings. One spring is thus removed from the operating path of thealternate spring, which latter spring causes the engagement of themovable contact with a stationary contact.

The invention will be better understood from the following descriptionand drawing in which Figs. 1 and 3 illustrate the two forms of thevacuum contact switch operating mechanism for the movable contact arm;and

Fig. 2 illustrates a ringing interrupter circuit using the vacuumcontact switch as an interrupter and spark-absorbing devices associatedwith the switch contacts.

In the illustrated embodiment of Fig. 1, a metal evacuated container forthe contacts is shown. This form of container is preferable for thecontact switch of the invention but any suitable material may be used inplace of metal. The stationary contacts 4 and 5 are supported within thecontainer by an insulated part 6 rigidly fastened to the container. Thelead wires 77 and 8 are suitably insulated from the metal container bythe use of sealed-in insulators 9 and it. A flexible metal diaphragm 2,which may be a corrugated disc or sylphon bellows, is sealed to thecontainer. This diaphragm acts as a support and fulcrum for the movablecontact arm 3, which is accurately positioned and sealed therein. Themovable contact arm 3 is conductively connected to the diaphragm whichis conductively connected to the metal frame- The conductor ll thereforeacts to electrically associate the movable contact in a circuit witheither conductor 1 or 8. Rod 34, having an insulated member 82 thereon.is adjustably connected to the movable contact arm 3 by threaded members35 and 36. The insulated member i2 is maintained under equal pressurefrom springs i3 and i l. Spring I5 is a combination member stresseddownward, having one section 16 extending downward to the cam 58 and asecond section 31 extending upward between the springs 83 and M. Therotation of the cam l8 on shaitlli causes section 31] to move upward anddownward for removing the pressure of springs it or i l on the memberIt. The alternate spring it or i3 not moved by the cam is thus free tooperate the contact arm 3 through link 34 by exerting pressure on memberit. Ac-

cording to the drawing, spring I! is first moved upward by pressure ofthe cam against spring ii to permit the contact arm 3 to be moved upwardunder the control of spring 14. The movable contact is thus associatedwith stationary contact I. In a second position of the cam It, themember 31 draws the spring H downward under the control of spring IS.The pressure of spring I4 is thus removed from spring 13, permitting thelatter spring to function for moving the contact arm I for connectingits contact with stationary contact 5. In each case, the movable contactarm is entirely under the control of either spring l3 or H, andconsequently a uniform contact pressure is obtained between the movablecontact and the stationary contacts 4 and I. This method of operationfurther insures minimum flexing of the diaphragm 2 upon each operationof the springs I3 and it, since the arm 3 can remain substantiallyrigid. In addition to this step to produce long life, a diaphragm withannular corrugations isused which in some cases may be in the form of asylphon bellows. This also eliminates the critical adjustment ordinarilyrequired between the cam and the movable arm to insure a given contactpressure.

It is evident from the foregoing description that the gram contactpressure of the movable contact against a stationary contact is equal tothe free stiflness characteristic of the spring I: or it, minus thestillness required to flex the diaphragm of the container, which acts asa fulcrum for the movable contact arm. The stiflness characteristic ofthe corrugated or sylphon bellows type metal diaphragm may be of a setvalue and consequently the stillness characteristic of the operatingsprings may be of set values for securing a particular gram contactpressure. It is also apparent that in the combination described, thediaphragm is only flexed a small amount equal to the movement of themovable contact arm, since the desired contact pressure is obtained bythe movement and pressure of the spring against the arm which may remainrigid whereas in the usual method the contact arm is operated bypressure from a rigid cam which must flex the movable arm andaccordingly flex the diaphragm more than required for the normalmovement of the arm.

Fig. 3 illustrates a second form of the mechanism for controlling themovable contact arm. The vacuum contact comprising members 40 to is thesame as shown in Fig. 1. The operating mechanism for the movable contactarm comprises a cam 5| centrally located between springs 54 and andoperated on cam shaft 52. The spring support 53 and cam shaft 52 are, ofcourse, held on the mounting or framework which also maintains thevacuum contact switch in position. The rotation of the cam Isuccessively moves spring 54 downward and spring I! upward. The movementof spring 54 downward permits motion of spring 55 for operating thecontact arm 42 and causing the engagement of the contact thereon withcontact 44. The upward movement of spring I causes spring 54 to actuatethe movable contact arm 42 for the engagement of the contact thereonwith contact 43.

The vacuum contact, according to either iorm of Fig. 1 or Fig. 3, isshown in Fig. 2 associated with a circuit for applying interruptedringing current in the manner used for telephone circuits. Thealternating current supply is shown diagrammatically at 24. A tonecircuit is superimposed upon the alternating current for the purpose ofslightly exaggerating the ringing tone for transmission to the callingtelephone subscriber. The tone source is shown diagrammatically at 12,which is transmitted to the ringing circuit through the primary andsecondary windings of transformer ii. The battery 25 is used in thiscircuit for maintaining apparatus operated when ringing current is notassociated with the telphone circuit. This is known to those versed inthe art as "silent period battery". The dotted lines and the rectangle28 indicate apparatus in a telephone exchange for applying the ringingcurrent to the individual subscriber stations, such as diagrammaticallyillustrated as ill. A plurality of such apparatus is used in a telephoneexchange and therefore multiple straps 28 and 21 are indicated to showthat the ringing interrupter circuit is common to a large plurality oftelephone circuits. According to this arrangement, when the movablecontact 3 is associated with the stationary contact 5, ringing currentfrom source 24 is applied to the sub scriber station ringer 30. When themovable contact is associated with the stationary contact 4, silentperiod battery is applied to the circuit for maintaining certainapparatus of the telephone exchange operated. As is well known, theringing current and silent period are successively applied until thesubscriber responds by removing the receiver from the subscriber stationset. In case the subscriber does not answer, the ringing current is cutoil by manual or automatic means.

It is the usual practice to use condensers and resistances to reducecontact arcing. In the present circuit arrangement, the use of acondenser would oifer a low resistance path to ringing current and tonessuperimposed on the fundamental voltages. An arrangement has, therefore,been devised using cold cathode glow discharge tubes 20 and 2| bridgedacross the contacts of the vacuum contact switch in series withresistances 22 and 23 for use as a current discharge device when thecontacts are separated. These tubes will flash momentarily when thecircuit is broken and thus permit inductive energy to be dissipated inthe resistance of the circuit and the internal resistance of the tubes.These tubes are arranged for a break-down voltage higher than thepotential normally across the open contacts. They also have a restoringvoltage of such character that the tube will extinguish itself as seenas the circuit voltage falls to normal. The resistances 22 and 23 alsoserve the purpose of protecting the tube from excessive current. Theforegoing arrangement protects the contacts from being pitted by theelectric arc and thus insures a comparatively long life for thesecontacts and exact contact engagement during their life.

It is not the intention to limit the invention to the specificstructures disclosed, since the principle may be applied in variousmanners.

What is claimed is:

1. An electric switch comprising an evacuated container having aflexible diaphragm formed as a part of said container, stationarycontacts in said container, a movable contact arm extending through saiddiaphragm and supported thereby, two springs having equal stillnessarranged to exert equal pressure in opposite directions on said movablecontact arm, and means for relieving the pressure of either one of saidsprings against said contact arm for operating 7 the'contactarm underthe control of the opposite spring.

2. An electric switch comprising an evacuated container having acorrugated flexible diaphragm formed as a part of said container,stationary contacts in said container, a movable contact arm extendingthrough said diaphragm and supported thereby, two springs having equalstillness arranged to exert equal pressure in opposite directions onsaid movable contact arm, and means for relieving the pressure of eitherone of said springs against said contact arm for operating the contactarm under the control of the opposite spring.

3. An electric switch comprising a metal evacuated container having acorrugated metal flexible diaphragm formed as a part of said container,stationary contacts in said container and insulated therefrom, a movablecontact arm extending through said diaphragm and electrically connectedthereto, two springs having equal stiffness arranged to exert equalpressure in opposite directions on said movable contact arm, and meansfor relieving the pressure of either one of said springs against saidcontact arm for operating the contact arm under the control of thealternate spring.

4. An electric switch comprising an evacuated container having aflexible diaphragm formed as a part 01' said container, stationarycontacts in said container, a movable contact arm extending through saiddiaphragm and supported thereby,

a pair of springs having equal stifiness, a memher under pressure ofsaid stiifness between said springs adjustably connected to said movablecontact arm, and means for relieving the pressure of either one of saidsprings against said mem-- her for operating the contact arm under thecon trol of the alternate spring.

5. An electric switch comprising an evacuated container having aflexible diaphragm formed as a part of said container, insulatedcontacts in said container, a movable contact arm extending through saiddiaphragm and sealed thereto, said diaphragm acting as a pivot memberfor the contact arm, means for operating said contact either arm in amanner to obtain an exact contact pressure between a contact on said armand the insulated contacts, including an adjustable mem-v ber connectingthe contact arm with an operating spring, a second spring for exertingequal pressure against said first spring for normally maintaining thespring inoperative, and means to remove the pressure of said secondspring for operating the contact arm under the control of said firstspring.

6. An electric switch comprising a movable contact arm, pressure membersassociated with said arm and arranged to exert equal and oppositepressures thereon, stationary contacts, and means for alternatelydisassociating said pressure members from said arm to cause said arm toalternately engage said stationary contacts.

7. An electric switch comprising a movable contact arm, pressure membersarranged to exert equal and opposite pressures on said arm, and meansfor alternately actuating said members to render the unactuated membereifective in actuating said movable arm.

8. An electric switch comprising a movable contact arm, a. firstpressure member arranged to exert a pressure in a particular directionon said arm, a second pressure member arranged to exert an equalpressure in the opposite direction on said arm and means for actuatingeither of said pressure members whereby the other pressure memberfunctions to actuate said contact arm.

9. An electric switch comprising an evacuated container having aflexible diaphragm formed as a part of said container, stationarycontacts in said container, a movable contact arm extending through saiddiaphragm and supported thereby, means comprising a pair at springs forapplying equal and oppositely directed forces to the extending portionof said arm whereby said arm is held in equilibrium and is pivotedabout.

its point of support on said diaphragm when of said springs is actuatedand means for alternately actuating said springs to cause it to engagesaid stationary contacts alternately.

O]? J. MEANS.

